UNIO. 



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'oval. 



*laticostasus. Lea. 



*hippopseus. Lea. 



OBLONG. 



*Sloatianus. Lea. Chenu. 

 Unio plectiforus. Con. 



dorsuosus. Gould. 



hylseus. If Orb. Schom. 

 Unio Guarianus. D' Orb. 



*trapezoides, Lea. Chenu. 



Unio crassidens. Lam. Var. a. 

 Unio interruptus. 1 Say. Desk. 



WIDE. 



*ellipticus. Lea. 



Diplodon ellipticum. 2 Spix. 

 Unio multistriatus. Lea. L'Orb. 

 Unio psammaticus. Bronn. 



cucumoides. Lea. Chenu. 



*subtentus. Say. Con. Lesh. 



WIDE. 



*Hembeli.. Con. 



Osbeckii. Phili. 



*Conradicus. Lea. 



*acutissimus. Lea. Con. Chenu. 



*Murchisonianus. Lea. 

 Unio Douglasise. 3 Gray. 



*Grayanus. Lea. 



Unio Grayii. Ln Griffith's Cuvier. 



ARCUATE. 



ponderosus. Lea. 

 Mya ponderosa. Solan. Dill. 

 Mya crassa. Wood. 



QUADRATE. 



*lacrymosus.' 1 Lea. Chenu. 



*asperrimus. s Lea. 



Unio quadrulus. Say. Con. 



*Rumphianus. Lea. 



1 Mr. Say, in his "Synonymy," claims precedence in this species, although my Memoir hears date May, 1830, 

 while his is December, 1831. (See Transylvania Journal, vol. v.) The reader will not, after this, be surprised to 

 be told that TVIr. Say does not allow me, in his very incorrect " Synonymy," to be the discoverer of a single new 

 species of Unio from our western waters ! ! I may be allowed also to state, that I do not understand why he gives 

 the same name to two of his different numbers: thus, he calls No. 17, U. interruptus, Rafm. ; and No. 47, U. inter- 

 ruptus, Say. The species are evidently distinct. 



a I have no doubt of D. ellipticum being the same with my Unio multistriatus, but it is a true Unio. Mr. 

 Barnes gave the same specific name to an American Unio, but it had been previously described by Lamarck as 

 ligamentinus. 



3 In Jardines's Mag. Zool. and Botany, vol. i. p. 285, Mr. Gray claims precedence for his name Douglasise. 

 He published it in Griffith's Cuvier, bearing the date of 1834. My description, published in the Trans. Am. Phil. 

 Soc, dates 1832. 



1 It is a matter of some doubt if this be more than a beautiful variety of asperrimus (nobis). Future observa- 

 tion must determine. Ferussac and some other zoologists believe it to be distinct. Dr. Ward says they "are cer- 

 tainly distinct." 



5 Mi. Say supposed this to be the rugosus, Barnes. Two specimens referred to by Mr. B. as rugosus were 

 under my inspection, and proved to be — the one a fiat metanevra, Rafin., the other a plicatus, Lesueur. Mr. B., in 

 his reclamation, recognizes his rugosus as U. Peruviana, Lam., which shell is undoubtedly the plicatus, Lesueur 

 and Say. 



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